Power semiconductors devices can deal with voltages of about 1.7 kV or higher. The semiconductor device and the base plate, which can be made of molybdenum or an alloy based on molybdenum, can be in surface contact to allow conduction of electricity and heat transfer away from the semiconductor, for example, the semiconductor device is thermally and electrically coupled to the base plate. Power semiconductor devices used in this area can be power transistors, for example, insulated gate bipolar transistors (IGBT), reverse conducting insulated gate bipolar transistors (reverse conducting IGBT), bi-mode insulated gate transistors (BIGT) or (power) diodes.
Power semiconductor devices can be combined for forming power semiconductor modules, which can deal with currents of up to 100 A or more. The power semiconductor devices can be arranged in parallel on a common base plate, which can form an electrically conducting base of the power semiconductor module. The power semiconductor module can be covered by an electrically conducting top plate, which can be a lid of a housing of the power semiconductor module. The top plate can provide a further contact for the power semiconductor devices. The power semiconductor modules can include identical power semiconductor devices, for example, power transistors, or different power semiconductor devices, for example, a set of power transistors and at least one power diode. The power semiconductor devices can be connected to the electrically conducting top plate by means of the presspins. In case of power transistors used in the power semiconductor modules, the control contacts can be connected to the lid by means of presspins, wherein the top plate can be electrically isolated from the control contacts.
Multiple power semiconductor modules can be combined to form a power semiconductor module assembly. The power semiconductor modules can be arranged mechanically and electrically in parallel to each other in a common housing. The base plates of the power semiconductor modules can form an electrically conducting base of the power semiconductor module assembly. Additionally, the housing of the power semiconductor module assembly can be covered by an electrically conducting lid, which can be in contact with the lids of the power semiconductor modules arranged therein. In an embodiment of the power semiconductor module assembly, the lid of the assembly can be a common lid for the multiple power semiconductor modules therein. The power semiconductor module assembly can include identical power semiconductor modules, for example, power semiconductor modules including power transistors and power diodes as described above, or different power semiconductor modules, for example, a set of power semiconductor modules including power transistors and at least one power semiconductor module including power diodes. Such power semiconductor module assemblies are, for example, known as “Stakpak” from the applicant and can be used for forming stacked arrangements as used for example in HVDC applications, which deal with up to several hundred kV. Accordingly, the mechanical design of the power semiconductor module assembly can be enhanced (e.g., optimized) in order to facilitate clamping in long stacks. In these stacked arrangements, mechanical and electrical stability of a single power semiconductor module assembly is desired to help prevent failures of the entire stacked arrangement.
Instead of arranging the power semiconductor modules in power semiconductor module assemblies and stacking of the power semiconductor module assemblies, the power semiconductor modules can also be stacked directly.
In a stacked arrangement of power semiconductor modules or power semiconductor module assemblies, a cooler can be provided between neighbouring power semiconductor modules or power semiconductor module assemblies. The coolers can use water as heat transfer medium for cooling the stacked arrangements of power semiconductor modules or power semiconductor module assemblies. The coolers can be relatively expensive to replace.
In the context of stacked arrangements, support of a short circuit failure mode (SCFM) of the individual power semiconductor devices can be a feature. In case one of the power semiconductor devices fails, the device can fail by providing a short circuit to enable conduction from the base plate to the lid, which can disable the power semiconductor device in SCFM. The same can also refer to the power semiconductor module assemblies including the failing power semiconductor module. When multiple of the power semiconductor modules or the power semiconductor module assemblies can be connected in series, for example, forming the above-mentioned stacked arrangement, failure of a single power semiconductor device does not lead to a failure of the stacked arrangement as a whole.
In this short circuit failure mode, currents of up to 2000 A can flow through a single power semiconductor device and the respective press pin in contact with the failing power semiconductor device, since the short circuit bridges all parallel power semiconductor devices. To achieve a high life time of these power semiconductor devices and accordingly a high life time of the power semiconductor modules and the power semiconductor module assemblies, it is desired that the short circuit failure mode can be maintained for a year or even more. In power semiconductor module assemblies, failure of a single power semiconductor module is not critical, since a neighbouring power semiconductor module can provide electrical connection between the two contacts of the assembly. Accordingly, internal damage of a power semiconductor module can be tolerated within a power semiconductor module assembly, even when all pins of a single module are consumed due to arcing.
Arcing within the power semiconductor device can also involve the top plate or lid. A top plate of a power semiconductor device can be made of copper, which can provide a good conductivity and can be produced at reasonable costs. Since the arcs can cause temperatures high enough to melt the top plate, the top plate underlies wearing and oxidation and can be even destroyed. For example, in a power semiconductor module assembly, when the top plate of a power semiconductor module is destroyed, the lid of the power semiconductor module assembly can also be affected by the arcing and thereby be destroyed. Accordingly, a failure of a single power semiconductor module can propagate to neighboring power semiconductor modules and can cause failure of the entire power semiconductor module. Furthermore, in a stacked arrangement of power semiconductor modules or power semiconductor module assemblies, the cooler between in contact with the top plate or the lid can also be affected by the arcing. For example, when the cooler is destroyed, water leakage can occur and cause further failures. Water leakage in electrical installations can also be a general safety problem, especially taking into account the high voltages and currents involved.